The simple expression of "detection" herein used is employed to mean conversion of light and radiation to electrical signals. The detection of light utilizes the photoelectric effect in which light of 300 nm to several .mu.m wavelength changes into electrical signals in semiconductor. The detection of radiation utilizes the mechanism in which ionizing radiation such as X-ray and r ray and charged particles generate electron-hole pair in semiconductor to produce electrical signals therefrom. A plurality of detection semiconductor arranged in one plane can detect two-dimensional information (surface resolution). FIG. 20 shows one example of the conventional semiconductor detector of charged particles. FIG. 20 (a) is a diagrammatic plan view of the detector,
FIG. 2 (b) is a diagrammatic section view on line A--A', and FIG. 2 (c) is a diagrammatic section view on line B--B'. In the Figures, the numeral 12001 indicates a semiconductor detector of charged particles, 12002 indicates the substrate thickness, 12003 indicates a p strip read-out capacitance electrode, 12004 indicates a p strip capacitance insulating film consisting of a capacitance insulating film, 12005 indicates an N- type Si (silicon) semiconductor substrate, 12006 indicates an n strip consisting of N+ type impurity layer with doping concentration of about the 19th to 20th power, 12007 indicates an n strip read-out capacitance electrode, 12008 indicates an n strip capacitance insulating film, and 12009 is a p strip consisting of P+ type impurity layer with doping concentration of around the 19th power of 10.
As is apparent from FIG. 20, a plurality of p strips 12009 are arranged in parallel in the shape of strip on the front side of the semiconductor substrate 12005. On the back side of the semiconductor substrate 12005, a plurality of n strips 12006 are arranged in parallel in such a direction as to cross the above mentioned p strips. On each p strip 12009 there are provide a p strip capacitance insulating film 12004 and a p strip read-out capacitance electrode 12003, while an n strip capacitance insulating film 12008 and an n strip read-out capacitance electrode 12007 are provided on each n strip.
FIG. 21 is a schematic circuit diagram showing a detection part of FIG. 20. 12001 represented with phantom line indicates an IC chip on which semiconductor detector of charged particles is formed. 12104 indicates a crossing part of the above mentioned p strip 12009 and the n strip 12006, at which a pn junction is formed to construct a detection diode which functions as detection part of charged particles. 12102 indicates a capacitance C.sub.G formed at both ends of the diode 12104, which constitutes a read-out capacitance. 12103 indicates a read-out amplifier and 12105 indicates the ground GND. 12106 indicates a bias resistance and 12101 indicates a bias power supply V.sub.B. Each detection diode 12104 is electrically connected to the bias power supply V.sub.B 12101 through the bias resistance 12106.
When bias power supply VB is applied, depletion layer is extended from the boundary of the reverse-biased pn junction in the direction of the substrate thickness 12002. The layer can be expanded to almost the same thickness of the substrate. If charges particles fall on the depletion layer, electron-hole pairs are generated inside the depletion layer, signals are produced through the read-out capacitance by an external circuit, such as a read-out amplifier 12103 in a quantity that is a measure of the incident charged particles. At this time, as the p strips on the front side and the n strips on the back side cross to form a detection diode 12104 at each crossing point as is described above, the output of the diode shows the position and the quantity of the incident charged particles. Such detector is a semiconductor device intended for detecting charged particles in real time (constantly).
As semiconductor devices for detecting lights, there are those using pn junctions or npn transistors arranged two-dimensionally as detection element (the examples of such devices are not shown in the drawings), other than CCD. In such devices, the signals are processed by selecting each elements in time division system.
Conventional semiconductor detectors with the structures described above have the following problems:
1. As structures such as capacitance and wiring have to be constructed on both sides of the semiconductor substrate, many process steps are required and fabrication process is complicated. Moreover a frequent occurrence of flaw on the surface due to the complicated double-side process makes the improvement in yield difficult and therefore increases the manufacturing cost.
2. The relationship between the thickness of the depletion layer which affects the detection and the quantity of the material which causes the multiple scattering limits the thickness of the semiconductor substrate used; in general, a thickness of 200 to 400 .mu.m is often employed, while a thicker substrate of 500 to 650 .mu.m cannot be used. This means that in semiconductor wafer process, state-of the art process technologies such as high-cleanness and high-resolution process cannot be used, because either of such process technologies uses a 6-inch or wider diameter which, if given a thickness of less than 500 .mu.m, has a high possibility to break and therefore is difficult to fabricate in the process.
3. For the detection of lights as well as for the detection of the charged particles, if pn junction only is used, the magnitude of the signal is so small that it is difficult to obtain a S/N (signal to noise) ratio high enough in relation to other capacitance and resistance to be added.
4. For the detection of lights as well as for the detection of the charged particles, if npn (or pnp) transistor structure is utilized, the amplification of the signal is performed by the detection element itself, therefore while the signal of large magnitude can be obtained, measurement (sampling) in high-speed (more than several MHz) is difficult due to the large junction capacitance and the long storage time of the minority carriers in the base region.
It is therefore an object of the present invention to find a novel principle to solve the problems above and to provide a novel high-performance semiconductor detector of light and radiation and the manufacturing method of the same based on this principle.